Struct DegradedLink 

pub struct DegradedLink<T> { /* private fields */ }

A [Transport] decorator that simulates an ongoing degraded link.

Where Faulty in pamoja-loopback fails a fixed number of upcoming sends, a DegradedLink models a link that stays bad, so offline-first behavior can be proven against a realistic pattern rather than a one-shot outage. It can drop a configurable fraction of sends (a lossy radio) and cycle between reachable and unreachable windows (a link that comes and goes). Both are deterministic - driven by a send counter, not a clock or randomness - so a store-and-forward drain over the link behaves the same way every run.

Connect and subscribe pass straight through; only send is degraded, since that is the path store-and-forward depends on. A degraded send returns [Error::Transport], which drain_to leaves buffered, in order, to retry later.

Examples

use pamoja_core::Transport;
use pamoja_loopback::{LoopbackBroker, LoopbackTransport};
use pamoja_sim::DegradedLink;

let broker = LoopbackBroker::new();
// A link that drops every second packet.
let mut link = DegradedLink::new(LoopbackTransport::new(broker)).drop_every(2);
link.connect().await?;

link.send("t", b"1").await?; // first send: delivered
assert!(link.send("t", b"2").await.is_err()); // second send: dropped
link.send("t", b"3").await?; // third send: delivered

Implementations

impl<T> DegradedLink<T>

pub fn new(inner: T) -> Self

Wraps inner as a perfect link, until loss or intermittency is added.

Arguments

• inner - the transport to decorate.

Returns

A decorator that passes every send through until configured otherwise.

pub fn drop_every(self, n: u32) -> Self

Drops one in every n sends, simulating a lossy link.

Arguments

• n - drop every nth send; 0 disables loss.

Returns

The updated link, for chaining.

pub fn intermittent(self, up: u32, down: u32) -> Self

Cycles between up reachable sends and down unreachable sends.

Sends rejected during a down window return [Error::Transport], the same as a real link that is temporarily out of range.

Arguments

• up - the number of sends that succeed at the start of each cycle.
• down - the number of sends that fail before the cycle repeats.

Returns

The updated link, for chaining.

pub fn into_inner(self) -> T

Unwraps the decorator, returning the inner transport.

Returns

The wrapped transport.

Trait Implementations

impl<T: Clone> Clone for DegradedLink<T>

fn clone(&self) -> DegradedLink<T>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug> Debug for DegradedLink<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: Transport + Send> Transport for DegradedLink<T>

async fn connect(&mut self) -> Result<()>

Establishes the connection to the broker, peer, or bus.

async fn send(&mut self, topic: &str, payload: &[u8]) -> Result<()>

Publishes a payload to a topic.

async fn subscribe(&mut self, topic: &str) -> Result<()>

Subscribes to a topic so that matching payloads are routed to this transport.